1. Viruses and Bacteria

2. What do these diseases have in common?
Mumps
Hepatitis B
Measles
Polio

3. It looks alive, acts alive… but its not!
Viruses are not living things. They differ from living things in several ways:
They need to be inside a living organism to reproduce themselves.
Outside the cell, they have no metabolism.
They do not have cell parts. (i.e. nucleus, mitochondria, etc)
They are composed of only a nucleic acid (DNA or RNA) inside a protein capsule.

4. Viral Reproduction In order to reproduce:
A virus attaches to a host cell.
The virus injects the cell with its nucleic acid.
The viral nucleic acid commands the cell to make more viral protein and nucleic acid.
The cell then ruptures, releasing hundreds of new viruses.

5. Retroviruses…No, they aren’t from the 70’s!
These are viruses that store their genetic information as RNA.
Their genetic information is copied backward-from DNA to RNA.
Ex: some types of cancer & AIDS

6. How it works…… They infect their host cell.
They produce a DNA copy of their RNA.
It may remain dormant for varying lengths of time.

7. Your friendly bacteria
Bacteria are living, unicellular prokaryotes.
Divided into two kingdoms: Eubacteria and Archaebacteria
Heterotroph or autotroph (most use chemosynthesis).
Types of Bacteria are classified based on their shape, type of cell wall, and movement.
Bacteria have three basic shapes:
Bacilli – rod-shaped
Cocci – spherical
Spirilla – spiral

8. Gram staining is used to differentiate types of Eubacteria.
Eubacteria have peptidoglycan and certain specialized lipids in their cells walls that are not present in Archaebacteria.
Gram staining is used to differentiate types of Eubacteria.
Those having thick cell walls will absorb more of the dye and appear dark purple (Gram positive).
Those having thinner cell walls will absorb less of the dye and appear pink (Gram negative).

9. Bacteria Growth and Reproduction
Bacteria reproduce in two main ways:
Binary fission – when a bacteria grows to double its original size, it copies its DNA and divides, producing two identical cells.
Conjugation – a hollow bridge is formed between 2 bacteria and genes are transferred from one cell to the other.
This creates genetic diversity within the population.
Spore formation – when conditions are unfavorable (lack of food, drought) that encloses its DNA and part of its cytoplasm in a spore.
When conditions are better, the spore will germinate, and the bacterium will continue to grow.

10. They’re not all bad….
Bacteria are most widely known for causing diseases such as strep throat, tetanus, meningitis, and tuberculosis.
However, most bacteria are very useful:
E. coli helps us digest our food & make vitamins for humans.
Many are important decomposers in our ecosystem.
Rhizobium provides plants with nitrogen.
A few bacteria are used to clean up small oil spills in the ocean.

11. Vaccinations
A weakened form of the pathogen (virus/bacteria) is used to stimulate the production of antibodies.
However, bacteria and viruses have very high reproductive rates, which result in many mutations.
Thus, bacteria and viruses evolve quickly, often requiring a different vaccine every year.

12. There are two types of vaccines (immunities):
Active – person is injected with the actual pathogen, and immune cells make their own antibodies against the disease, immunity is permanent
Passive – person is injected with antibodies that fight the disease, but immunity is temporary